Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
The typical construction of a wind turbine involves erecting the tower and then connecting various other components to the erected tower. For example, the rotor blades may be lifted to an appropriate height and connected to the tower after erection of the tower. In some cases, each of the rotor blades is connected to a hub before lifting, and the connected rotor blades and hub are then lifted and connected to the tower as a unit.
Current methods and apparatus for lifting the rotor blades involve the use of cranes. Typically, a main crane lifts a rotor blade or a plurality of rotor blades connected to a hub to the appropriate height. These components are then connected to the tower, and the main crane is then disconnected from the components.
In some cases, an auxiliary crane, sometimes referred to as a tail crane or tail pick crane, is additionally utilized. The auxiliary crane is connected to a rotor blade to control movement of the rotor blade during lifting, thus preventing the rotor blade from striking the tower or the ground or otherwise damaging any wind turbine components. To disconnect the auxiliary crane from the rotor blade, the cables coupled to the rotor blade are slid in a generally span-wise direction towards and past the tip of the rotor blade. As the cables pass the tip, the auxiliary crane is disconnected from the rotor blade.
However, disconnecting the auxiliary crane from the rotor blade in this fashion can have disadvantages, and may damage the rotor blade. For example, current advances in rotor blade technology have led to the installation of various blade appendages, such as noise reducers, lightning receptors, and vortex generators, on the exterior of the rotor blades. When the cables of the auxiliary crane are slid in the generally span-wise direction, the cables may encounter and contact these appendages. Such contact can damage the appendages and the exterior surfaces of the rotor blade.
Thus, an improved lift system and method for constructing a wind turbine are desired in the art. For example, a lift system and method that may prevent rotor blade damage during lifting and connecting of the rotor blades would be advantageous.